Pathogenesis of Infectious Diseases - KSU

Pathogenesis of Infectious Diseases

CLS 212: Medical Microbiology

Definitions

? Path- means disease. ? Pathogenesis The steps or mechanisms involved in the development of a

disease. ? Infection The presence and colonization of a pathogen in human body. ? Infectious Disease Is a disease caused by a pathogen (microorganism).

? Not all pathogens entering human body will cause disease because humans are protected by normal flora and the immune system.

Course of an Infectious Disease

There are 4 phases or periods in any infectious disease: 1. The incubation period: The time between entry of the pathogen and the onset of

symptoms. 2. The prodromal period: The time when the person feels abnormal and week. 3. The period of illness: The time when the person feels typical symptoms associated

with that specific disease. 4. The convalescent period:

The time when the person recovers from the infection but may develop permanent damage to the area of infection.

Localized vs. Systemic Infection

Localized Infection The pathogen is only present at the original site of infection (eg. Pimples or abscesses)

Systemic Infection (Generalized) The pathogen is carried to other parts of the body by blood, lymph,..

Acute, Subacute, and Chronic Disease

Acute Disease Rapid onset of disease and rapid recovery.

e.g. Influenza, measles,..

Chronic Disease Slow onset of disease and last a long time.

e.g. Tb, syphilis,..

Subacute Disease The disease with onset less than acute but more than chronic. e.g. bacterial endocarditis.

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